Home automation or management systems which permit increased control of at least some of the electrical subsystems in a dwelling have begun to replace or to supplement conventional wiring systems. These systems can provide automatic control of or can provide increased user control options for such systems as electrical power and lighting, heating ventilation and air conditioning, audio/video home entertainment systems, security systems, telecommunications equipment, and landscape maintenance systems such as automatic lawn sprinklers.
Many home control systems and lighting control systems or subsystems are generally incompatible with conventional wiring techniques. One common complaint is that the additional wiring required for such system results in a maze of additional wiring. The systems also tend to be relatively expensive. It is desirable, therefore, to have a wiring device that is compatible with existing wiring, and requires only the addition of easy to install low voltage wiring during initial construction. One such system is disclosed in U.S. patent application Ser. No. 08/303,985 in the name of Charles Winterble and filed concomitently herewith.
Another example of a lighting control system is the remote control low voltage switching system manufactured and sold by General Electric. Components of this system include transformers or power supplies, relays and remotely positioned low voltage switches. The relays include a split low-voltage coil to switch a line voltage contact armature between the on and off positions. These relays are mechanical latching type relays which are switched by momentary 24 volt rectified AC switch circuit pulses. A class 2 transformer supplies 24 volt DC current to the switching circuit of the relay and one or more remotely located low voltage switches can be used to switch each relay. The relays are discrete components which can be mounted in an electrical wall box. Similarly the switches are discrete components. Each relay has line voltage screw terminal located on the main body of the relay and class 2 control leads extending from the top of a tubular housing containing the relay coil. This relay can be mounted in one of the round knockouts of an electrical box with the tubular housing extending through the knockout hole. The connection between these leads and the class two wiring would be made using conventional wirenuts of quick disconnect terminals on the exterior of the device box. Typically several relays are placed in the same central location. The low voltage switches used to provide a momentary input to the relays are remotely located relative to the relay which they control. For example, if five relays are wired in parallel with the power supply, the maximum switch leg between a switch and a relay would be 240 feet, assuming that 20 AWG control wiring is used.
Another example of a lighting control system which uses low voltage remote control for switching lighting fixtures is the system disclosed in U.S. Pat. No. 5,191,265. A commercial version of that device is the Grafik Eye 3000 and 4000 Series Preset Dimming Controls manufactured and sold by Lutron Electronics Co., Inc. Grafik Eye is a trademark of Lutron. Versions of that device can be mounted in two, three, or four gang electrical device boxes. Two banks of screw terminals are located on the rear of that device. One bank is used to connect the device to a source of line voltage and to loads. The other bank can be connected to low voltage remote controls. Apparently because of the size of that device and the use of multigang boxes, the line voltage and low voltage lines can be sufficiently separated.
In accordance with the National Electric Code (NEC), electrical conductors including electric light, power, class 1, or non power-limited fire protection signaling conductors must be separated from electrical conductors including power-limited class 2 or class 3 conductors. For purposes of this disclosure the power limited conductors will be collectively referred to as the first group of conductors and the class 1 and related conductors will be collectively referred to as the second group of conductors. The conductors of class 2 and class 3 or first group circuits cannot be in any cable, cable tray, compartment, enclosure, outlet box, raceway, or similar fitting with conductors from the second group conductors.
In accordance with the NEC conductors of the first group in cables, cable trays, enclosures, and raceways shall not be placed in any cable, cable tray, enclosure, or raceway or similar fitting with conductors of the second group. One exception to this is where the conductors of the different groups are separated by a barrier. Another exception is conductors and compartments or enclosures, outlet boxes or similar fittings where the first group of conductors are introduced solely to connect to the equipment connected to the first group of conductors.
The NEC further requires that all joints, connections and splices of electrical cables must be made inside an approved enclosure and further must include tight connections with the conduit or cable. Conventional electrical boxes may be made from metal or plastic. The box is further designed with great flexibility so that wires can be brought in from any side by removing a "knock out" to receive a lug for mounting fixtures or the like. In accordance with the present invention, the electrical box needs to include a knock out in the back of the box and additionally needs to be of sufficient depth to accommodate the wires of either a conventional device or a smart device.
While metal boxes are suitable for use with metallic or nonmetallic cable and conduit, nonmetallic boxes may only be used with nonmetallic cable and conduit. Plastic, polyvinyl chloride and fiber glass boxes are particularly popular as is the use of nonmetallic cable such as (NM, or NMC), commonly referred to as Romex cable. A grounding wire is also used with nonmetallic cable to provide proper grounding through the system. Nonmetallic boxes offer additional flexibility in that the material can be readily drilled to provide a cable receiving hole of the proper diameter at any desired location.
The present invention is designed to be compatible with the wires in a standard three way switch system having hot, neutral, switched hot and ground wires. In connecting the smart switch, the corresponding wires are interconnected with wire nuts. The remote control data wires are then connected to the stored remote control wires. It can be recognized from the standard three way wire system that having two power cables each with essentially four wires gets rather crowded when assembling the switch or device in the box. It is therefore necessary in accordance with NEC to have the barrier between the remote control data wires to have the required separation between the group 1 and group 2 wires. The three way wiring system allows a light or other devices to be switched on and off at more than one location. The same capability can be provided by using the smart wiring device which can be switched at the immediate location or from a remote control box via the data wire.